4-68-12.5D Centrifugal Fan

This article's table of contents introduction:

1. Decoding the Model Number
2. Typical Performance & Specifications
3. Key Design Features of the 4-68 Series
4. Maintenance & Operational Considerations
5. Common Use Cases for a 12.5D
6. Summary for Procurement or Replacement

The query "4-68-12.5D Centrifugal Fan" refers to a specific model of industrial centrifugal fan, commonly used in China and other markets for heavy-duty ventilation, dust removal, and air handling systems.

Here is a breakdown of the nomenclature and the typical specifications for this fan.

Decoding the Model Number

• 4-68: This is the series designation.
  • 4: Represents the fan’s pressure coefficient (multiplied by 10).
  • 68: Represents the specific speed of the fan.
  • Context: The 4-68 series is a classic design for medium-pressure, high-efficiency centrifugal fans, often used in dust removal systems with bag filters or cyclone separators.
• 5: This is the impeller diameter in decimeters.
  • 5 dm = 1250 mm (approx. 49.2 inches). This is a large industrial fan.
• D: This indicates the drive type.
  • D-Type means the impeller is overhung on the shaft and directly driven by the motor via a flexible coupling (not belts). The motor is typically mounted on a common base frame.

Typical Performance & Specifications

Note: These are generic values for a 4-68 series 12.5D fan running at standard conditions (20°C, 1 atm, density 1.2 kg/m³). Actual data depends on the specific manufacturer and rotation speed (usually 730 RPM or 960 RPM for D-type).

Key Design Features of the 4-68 Series

• Airfoil Impeller: The 4-68 fan usually has backward-curved, airfoil (wing-shaped) blades.
  • Pros: High efficiency (up to 85-90%), low noise, non-overloading power curve (motor won't burn out if duct is blocked).
  • Cons: More expensive to manufacture; blades can be sensitive to highly abrasive dust (wear).
• Housing: Spiral volute casing made of carbon steel (Q235) or wear-resistant steel.
• Inlet: Often includes a conical inlet cone for smooth airflow into the impeller.
• Drive: D-type requires precise alignment between the motor and fan shaft via a coupling. It runs at a fixed speed.

Maintenance & Operational Considerations

• Bearing Temperature: Always monitor bearing temperature. Max allowed is usually 80-90°C (ambient dependent).
• Vibration: Due to the large size (12.5D), vibration sensors (or at least dial indicators) are critical. Check for imbalance caused by dust build-up on blades.
• Rotor Balance: The impeller must be balanced (dynamic balancing) before operation. Dust will unbalance it over time.
• Ductwork: Ensure the inlet and outlet ducts are properly supported. Do not let the duct weight sag on the fan housing flanges.

Common Use Cases for a 12.5D

Because of its size and power, a 4-68-12.5D is typically found in:

• Centralized Dust Collection: For a large factory (woodworking, cement, grain silos).
• Boiler Induced Draft (ID): Medium-pressure draft for medium-sized industrial boilers.
• Mine Ventilation: In large tunnels or mine shafts (though axial fans are more common for pure ventilation).
• HVAC: Not typical for comfort HVAC; this is strictly industrial.

Summary for Procurement or Replacement

If you are buying or replacing this fan, you need to confirm with the manufacturer:

1. Rotation Speed (RPM): 730 or 960?
2. Motor Power: (e.g., YKK series 90kW 6-pole?).
3. Rotation Direction: Clockwise or Counter-clockwise (seen from drive side).
4. Discharge Angle: (e.g., 0°, 90°, 180° - where the air goes out).
5. Media: Is it clean air or dusty/gritty air? (If dusty, you might need a wear-resistant lining or a different series like 9-19 or M6-31).

Would you like me to recommend a specific motor power for a given airflow/pressure requirement?